In fields using a liquid-droplet ejection device such as an inkjet printer, a liquid droplet may not be ejected normally from a nozzle and abnormal ejection thus occurs when dust, bubbles, or the like is mixed in a flow passage including a nozzle during use of the liquid-droplet ejection device. When the abnormal ejection occurs, an amount of a liquid droplet ejected from a nozzle may decrease or a liquid droplet may not be ejected from a nozzle. Accordingly, conventionally devices capable of detecting whether abnormal ejection occurs in a plurality of nozzles have been suggested.
Japanese Patent Application Laid-Open No. 2008-168565 discloses an inkjet head that ejects a liquid droplet of ink. The inkjet head includes a plurality of nozzles, a plurality of pressure generation chambers communicating with the plurality of nozzles respectively, and a plurality of piezoelectric elements applying a pressure to ink stored in the plurality of pressure generation chambers. Each of the plurality of pressure generation chambers is provided with a heating element that heatsink stored in each pressure generation chamber and a temperature sensor that detects the temperature of the ink.
To detect abnormal ejection of a nozzle, ink is ejected from the nozzle communicating with the pressure generation chamber while the heating element heatsink stored in each pressure generation chamber. At this time, when a liquid droplet is normally ejected from the nozzle, a temperature of the ink stored in the pressure generation chamber gently increases due to the fact that the ink flows in the pressure generation chamber. However, when the abnormal ejection occurs in the nozzle, a temperature of the ink in the pressure generation chamber sharply increases due to the fact that the ink flows less in the pressure generation chamber. Accordingly, based on a change in a temperature of ink in the pressure generation chamber detected by a temperature sensor, it can be detected whether abnormal ejection occurs in a nozzle.